Refining of crude fats and fatty oils



I Patented July 14, 1936 DEFINING or cams m'rs AND mm on.s

Eric William Fawcett, Northwich, England, assignor to Imperial Chemical Industries Limited, a corporation or Great Britain No Drawing. Application May 9, 1935, Serial No- 20,69.l.. In Great Britain May 11, 1934 9 Claims. (01. 87-12) This invention relates to the refiningof crude fats and'fatty oils, for example linseed oil, cotton seed oil, ground nut oil, palm oil, whale oil and the like, and more particularly to the rehave found that the employment of so-called molecular distillation (by which is understood distillation under extremely low pressures and with the distilling and condensing surfaces a 55 distance apart of the same order as the mean free path of the molecules of the substance being distilled under the particular pressure employed) enables some separation by distillationto be effected, but does not give altogether satisfactory process, as, with acid breakingl do not require to employ the customary alkali wash, and with alkali breaking, I need only use the very small quantity of the alkali sumcient to achieve re moval of the mucilage etc., i. e. I may if demoval therefrom of the undesired impurities such results, inasmuch as a substantial proportion of a as free fatty acids, colouring matter and resinous the crude fat or oil appears in the first runnings or vegetable matter. 3 or remains in the residue, both of which have In the ordinary method of refining crude vegeundesirable properties, while the main fraction table oils and fats, it is customary to remove the also leaves something to be desired in the way 0 break by a treatment with alkalis, acids or of quality, I 10 salts. This removes certain mucilages, proteids -I have now found, that high grade products and non-oily constituents or impurities of" the maybe obtained in excellent yield by first breakcrude oil. For the present purposes an oil so ing the fat or oil by any suitable known proctreatedmay be called a broken oil. In further ess, and then submitting the broken fat or oil N treatments it is usual ,to submit the broken fat to short-path distillation under high vacuum. or oil to a bleaching operation, employing for By high vacuum is to be understood a vacuum example, absorbents such as fullers earth or acof the order of 10-? to 10- meet mercury, tive charcoal, and finally to deodorize the oil by and by short path distillation under condidlstillation insteam, with or without the emtions such that the oil distills without ebulployment of a vacuum. For high grade products, lition-from a heated surface and is condensed 20 alkali breaking is almost universally employed, on a condensing surface in a very close proximand in making neutral oils, which are ordinarily ity to the heating surface, namely, some 1-5 cms. what is wanted, it is customary to employ an exdistant. When the distance between the concess of alkali, i. e. sufficient to neutralize the densing and heating surfaces is less than the free fatty acids contained in the fat or oil as well mean free path of the molecules of the substance 25 as to remove the mucilage, the mixture of soaps, being distilled, the distillation is sometimes called impurities, and excess of aqueous alkali settling molecular distillation and under such condiout as foots. The foots are removed and the oil tions the rate of distillation is greater than when dried by heating. Other methods of breaking the said distance exceeds the mean free path.

0 are little used for high-grade edible fats or oils For a complete description of methods and ap- 3@ or drying oils; further, when acid refining is used, paratus for high vacuum or molecular distillait is usually regarded as essential to follow it with tion, reference is made to U. 5. Patent No. 1,955,- an alkali treatment, to remove the acid employed 321 to Burch et a.l., issued April 17, 1934, entitled for breaking and some or all of the fatty acids of Vacuum distillation. The apparatus therein dethe fat or oil. scribed can be utilized in carrying out the proc- 35 The term mucilage means mucilaginous or asses of the present invention. U. S. Patent No. gummy matter including any other solid or semi- 1,950,830, issued March 13, 19361 to van Dijck, solid 'colloidal matter which separates from the disclosesanother type of molecular still which crude fat or fatty oil as a result of the treatments can be used in carrying out my processes.

40 described, but excluding the free fatty acids In general, impurities such as free fatty acids, 40

which come out as soaps. ,That is, the noncolouring matter, etc. distill oii first at a conponifiable and non-fatty impurities in the oil siderably lower temperature than the triglyceror fat are the mueilage. I i ides, and if necessary the latter may be distilled Hitherto it has not been possible to remove the on at a. higher temperature from other impuriundesired impurities from crude fats and fatty ties such as resinous or vegetable matter.; 45 oils by distillation methods, owing to the decom- My process enables me to dispense with some position of the desired refined fats and oils at of the operations used in existing refiningtechthe temperatures required for the distillation nique, and to efiect purification by distillation even. when the distillation is carried out by means without decomposition of the triglycerides. Furof the usual vacuum distillation technique. I ther, I may use a relatively cheap breaking 50 sired dispense with the customary excess designed also to neutralize the free fatty acids. The breaking step is necessary prior to distillation, partly because it avoids mechanical troubles which might be caused by the presence of mucilage etc., in the short path still, but more so because it appears to assist the distillation in some way, at present not fully understood. as evidenced by the superior yield and quality of the final product. This is a remarkable eflect in view of the very small quantities of breaking substances which need be used; proportionsof the order of one part reagent to 1000 parts oil. Such small proportions are far insufilcient to eiIect any appreciable neutralization of free fatty acids or saponification of the neutral oil.

Example 1 A raw Egyptian cottonseed oil was broken by treatment with 0.1 per cent by weight of 50 per cent NaOH solution for one hour at C., with stirring. After cooling, the oil stood for 6 hours to allow the mucilage to settle. (This period could be shortened by centrifuging or filtration.)

The clear oil separated from the mucilage by filtration or decantation was distilled in a short path still, under a vacuum of 10- to 10- mms. of mercury and with a separation of 1.5 cms. between the heating and condensing surfaces. The first runnings, distilled off at about 200-220 C., comprised rather less than 5 per cent of' the total oil distilled; this fraction was dark-coloured, and contained also the free fatty acids of the original oil. The remainder of the oil was distilled at 250-260 C., at which temperature the oil completely distilled except for about 5 per cent of a dark tarry residue. Some per cent of the oil was obtained in this main fraction, which was a water-white oil, almost tasteless and odourless, and having an acid value of 0.l0.2.

Naturally, instead of obtaining one main distillate in this way, the distillation could be carried out to give a number of fractions if fractions of special properties. e. g. with reference to viscosity, melting point, drying properties, etc. were required.

By distilling the raw 011 without first breaking it, a muchlarger discoloured first fraction is obtained, as much as 15-20 per cent, while the main fraction in addition to being a correspondingly smaller proportion of the total oil distilled, is markedly inferior in colour, taste, and smell to that obtained from the broken ofl. Further, separation of mucilage in the still may give rise to operating difiiculties'such as splashing.

Example 2 tilled oil at about 210 C. The main fraction,-

removed at 250-260 C. and comprising around 90 per cent of the total oil fed to the still, had properties similar to those of the corresponding fraction described in the previous example.

Example 3 A raw Indian linseed oil (iodine number about was broken with 0.1 per cent by weight of alkali, mucilage removed, and the oil distilled as in Example 1 or 2. After removing the colouring materials and free fatty acids in the first fraction (200-220 0.), the principal distillate (MO-260 C.) was a very pale yellow oil having excellent drying properties.

Example 4 A crude whale oil was broken with 0.1 per cent by weight of caustic soda solution, the mucilage, etc., removed, and the oil distilled in a shortpath high vacuum still. After removing colouring matter and fatty acids in a first fraction, amounting to rather less than 10 per cent of the oil, at 200-210 C., the principal distillate (225- 260 C.) was an almost colourless oil free from the unpleasant smell and taste of the original oil, and amounted to about. 85 per cent of the initial oil.

I claim:-

1. Process for refining crude fats and fatty oils to secure in high yield a. refined fat or oil which comprises subjecting the fat or oil to a breaking treatment vflth a small amount of alkaline agent, separating impurities and submitting the thus treated material to distillation under a high vacuum corresponding to a pressure lower than about 0.01 millimeter of mercury and under short path conditions and at such temperature as to cause distillation of a relatively small fraction containing concentrated therein fatty acid impurities.

2. Process for refining crude fats and fatty oils to secure a refined fat or oil in high yield, which comprises subjecting a fat or oil to a small amount of mineral acid, separating impurities, and submitting the thus treated fat or oil to distillation under a high vacuum corresponding to a pressure lower than about 0.01 millimeter of mercury under short path conditions and at such temperature as to cause distillation of a relatively small fraction containing concentrated therein the free fatty ;acids of the fat or oil.

3. Process according to claim 2 wherein the fat or oil, after treatment with acid, is treated with alkali.

' c. The process of claim 5 in which the raw material is a vegetable fatty oil.

5. Process for refining fats and fatty oils from which break has been removed, to secure in high yield a purified fat or oil, which comprises subjecting the fat or oil to distillation under a high vacuum corresponding to a pressure lower than about 0.01 mm. of mercury under mart path conditions and under such temperature as to cause distillation of a small fraction containing fatty acid impurities concentrated therein, leaving a large residue of purified fat or oil.

6. Process for refining crude fats and fatty oils to secure in high yield a purified fat or oil which comprises submitting a crude fat or oil to a breaking treatment with-a reagent for removal of impurities, removing impurities and subjecting the fat or oil to distillation under a high vacuum corresponding to a pressure lower than about 0.01 mm. of mercury and under short path conditions at a low temperature to distill of! a small proportion containing fatty acid impurities concentrated therein, and then subjecting the remaining fat or oil to distillation under similar conditions but at a higher temperature suificient to cause the tri-glycerides to distill ofl and recovering such tri-glycerides, leaving a small residue.

7. Process for refining crude fats and fatty oils to secure a refined fat or oil in high yield which comprises subjecting the fat or oil to a breaking 7 treatment with a modicum of alkaline agent surflcient to modify mucilage in the starting material and cause separation thereof but insuflicient to neutralize the free fatty acids in the starting material, separating mucilage impurities and submitting the thus treated material to distillation under a high vacuum corresponding to a pressure lower than about 0.01 mm. of mercury and under short path conditions and at such temperature as to cause distillation of a relatively small fraction containing concentrated therein the free fatty acids of the fat or oil.

8. In the manufacture of neutral oils from oils containing free fatty acids and non-fatty impurities the process which comprises treating the oil with a minimal amount of caustic alkali solution in the amount necessary to cause a separation of non-fatty impurities, removing the separation and exposing the residual oil to short path distillation under conditions distilling over free fatty acids.

-9. Process set forth in claim 6, in which the reagent used for the breaking treatment is an alkaline reagent.

ERIC WILLIAM FAWCETI. 

